The 10th Gen uses preferred cores, it's meant to prolong cpu life by using up a couple cores first, and when they degrade, rotate out the preferred. But that also means the cpu has a tendency to not run as many cores as possible which under some circumstances the 9900k full cores usage is a benefit.
The other benefit being lga115x is proven, it's aged, matured and known. Like AM4 changes, lga1200 longetivity is still a relative unknown.